The air in the boys’ locker room was thick with chlorine and mildew, the showers silent. Izuku’s sneakers squeaked on the tile as he shifted his weight, his backpack clutched to his chest like a shield. “Kacchan?” The name was a whisper, a secret exhaled into the damp space. “Can I… can I have my third lesson?”

Katsuki leaned against a bank of lockers, his arms crossed. The fluorescent light cut harsh angles across his face. “Eager.” It wasn’t a question. He pushed off the lockers, the sound of his dress shoes deliberate on the floor. “Today’s lesson is about your mouth. Its purpose.”

Izuku’s breath hitched. He watched, transfixed, as Katsuki’s hands went to his belt. The click of the buckle was deafening. The zip of his trousers was a slow, tearing sound. “A blowjob isn’t about taking,” Katsuki said, his voice a low, instructional growl. “It’s about surrender. Your mouth isn’t yours. It’s a sheath. You understand?”

He pushed his trousers and briefs down just enough. His cock, heavy and thick, rested against his thigh. It was soft, but immense even then—a promise of what was to come. “Touch it.”

Izuku’s fingers trembled as he reached out. He laid his palm against the warm, velvety skin. It was so soft. He could feel the dense weight of it, the blood beginning to stir underneath his touch. “Use both hands. Learn the shape.”

Izuku obeyed, his smaller hands barely able to circle the girth. He stroked tentatively, up and down, feeling the skin shift. He watched, mesmerized, as it began to swell, thickening and lengthening in his grasp, the foreskin slowly retracting. It was alive, pulsing as it hardened, until he was holding a rigid, veined column of heat. Precum beaded at the slit, a clear, viscous pearl.

“See that?” Katsuki’s voice was tight. “Taste it.”

Izuku leaned in, his heart hammering against his ribs. He extended his tongue, a shy pink point, and swiped it over the head. The taste was salt and musk and something uniquely Kacchan—sharp, clean, male. A low groan rumbled from above him. “Good. Now down the shaft. Slowly. Learn the texture with your tongue.”

Izuku did. He licked a slow, wet stripe from the crown down the throbbing underside, tracing a prominent vein. The skin was smoother here, hotter. He followed it all the way down, his nose brushing coarse blond curls, until his tongue met the heavy, tight sac beneath. Katsuki’s thighs tensed. “Suck them. Gently. Just take one into your mouth.”

Izuku opened his lips, letting the firm weight of a testicle press against his tongue. He suckled softly, experimentally. The musk here was deeper, earthier. He heard Katsuki’s sharp inhale, felt a hand come to rest on the back of his head, not pushing, just holding. Guiding. “You’re a natural,” Katsuki breathed, the words strained. “Your mouth was made for this. For me.”

The hand in his hair tightened just slightly. “Now. The cock. Open wide.”

Izuku looked up, his green eyes wide and wet, his lips glistening. He opened his mouth, a silent ‘O’. The head, broad and flushed, pressed against his lips. It was too big. It would never fit. “Relax your jaw,” Katsuki commanded, his thumb stroking Izuku’s cheek. “Don’t think. Just feel it. Take what I give you.”

The pressure increased. The hot, smooth crown pushed past his lips, stretching them. Izuku’s tongue flattened underneath it, his mouth flooding with the taste of salt and skin. He made a soft, choked sound around the intrusion, his eyes fluttering shut. It was an overwhelming fullness, a claiming. He’d never felt so perfectly, terrifyingly used.

The hand in his hair tightened, a firm, undeniable pressure. "Deeper," Katsuki growled, his voice rough with restraint. "Take more. You're just tasting it. I want you to feel it in your throat."

Izuku whimpered, the sound vibrating around the thick intrusion. He tried to relax his jaw further, letting the heavy weight push past the initial resistance. The broad head nudged the back of his mouth, a blunt, impossible pressure. Tears welled in his eyes.

"Breathe through your nose," Katsuki instructed, his thumb stroking the hinge of Izuku's jaw. "That's it. Now swallow. Let your throat open for me."

Izuku swallowed reflexively. The muscles clenched, then yielded, and suddenly the crown was pressing into his tight esophagus. The stretch was breathtaking, a burning, full sensation that erased every other thought. He gagged, his body convulsing.

"Good," Katsuki praised, his hips shifting minutely, feeding another inch into the wet, clutching heat. "Your throat is so tight, Izuku. Perfect. Made for this."

Izuku's hands, which had been limp at his sides, came up to clutch at Katsuki's thighs. The wool of his trousers was rough under his fingertips. He focused on the smell of him—clean cotton, sharp cologne, and the deeper, musky scent of his skin and arousal. He focused on the low, approving sounds rumbling above him.

"Now pull back," Katsuki commanded, easing the pressure on Izuku's head. "Slowly. Use your tongue on the way out."

Izuku obeyed, sliding his mouth back until just the head rested on his tongue. His lips felt bruised, stretched. He swirled his tongue around the sensitive ridge, lapping at the fresh precum that seeped from the slit.

"Again," Katsuki said, and guided him back down. This time, the path was slicker, easier. Izuku took him deeper, his nose pressing into the coarse blond curls at the base. He held there, his throat fluttering wildly around the intrusion, his lungs screaming for air.

Katsuki's control was a live wire. Izuku could feel the tremble in the thighs under his hands, could hear the ragged pull of breath above him. "You learn fast," Katsuki muttered, his fingers carding through green curls. "Your mouth is getting so good. So greedy for it."

He set a rhythm then, not frantic, but deep and relentless. Guiding Izuku's head forward, letting him pull back, each stroke a little smoother, a little deeper. The wet, obscene sounds of sucking and gagging filled the silent locker room, punctuated by Katsuki's sharp grunts and Izuku's choked, willing whimpers.

"Look at me," Katsuki ordered, his voice thick.

Izuku forced his tear-filled eyes open, looking up the long line of his teacher's body. Katsuki's crimson gaze was locked on him, blazing with possessive heat. Watching himself disappear into the boy's mouth. The eye contact sent a shocking bolt of pleasure straight to Izuku's core, his own neglected pussy clenching around nothing, soaking through his uniform pants.

"You see this?" Katsuki breathed, his hips giving a shallow thrust. "This is what you're for. This is your third lesson. Your mouth belongs to my cock. Say it."

Izuku tried to speak around the fullness, producing a garbled, wet sound. Katsuki pulled him off until just the tip remained. A string of saliva connected Izuku's swollen lips to the glistening head. "It… it belongs to you, Kacchan," Izuku gasped, the secret name a prayer.

A feral grin touched Katsuki's lips. "Good boy." He pushed Izuku's head back down, burying himself to the hilt, and held him there. Izuku's throat worked desperately, his body shaking with the effort to take it, to please. Just as black spots danced at the edges of his vision, Katsuki pulled him free.

Katsuki let him breathe, his own chest rising and falling in a controlled rhythm. He looked down at Izuku, who was on his knees, lips swollen and slick, tears cutting clean tracks through the freckles on his cheeks. "You're a cocksucker now," Katsuki stated, his voice a low, dark rasp. "My personal cocksucker. And I'm going to fuck that pretty mouth until you forget how to speak without my cock in it."

His hands, large and unyielding, framed Izuku's face, thumbs pressing into the hinges of his jaw. "Open. Wider."

Izuku sobbed a breath and obeyed, tilting his head back, presenting his wet, reddened mouth. Katsuki didn't guide him this time. He positioned the broad, leaking head at his lips and, with a brutal snap of his hips, sheathed himself to the root in one savage thrust.

The sound Izuku made was a wet, guttural choke, instantly muffled. Katsuki held himself there, buried in the tight, fluttering heat of his throat, watching the boy's eyes roll back. "That's it," he growled, pulling back until just the tip remained, then slamming home again. "Take it. You're just a cocksleeve. A warm, wet hole."

He set a punishing pace, fucking into Izuku's face with deep, piston-like drives. The locker room echoed with the obscene, rhythmic sounds of flesh meeting flesh, of gagging, of spit and precum dripping onto the tile. Izuku's hands scrabbled weakly at Katsuki's thighs, his body convulsing with each invasion, tears and saliva streaming down his chin.

"Look at you," Katsuki snarled, his composure fracturing into raw hunger. "You're a mess. A perfect, filthy mess. My little fleshlight." He gripped a handful of green curls, yanking Izuku's head back to force agonizing eye contact. "You feel that? That's my cock rearranging your throat. Making it mine."

Izuku couldn't speak, couldn't breathe around the massive thickness stretching him open. His vision swam, his pussy aching and dripping, a traitorous pulse of heat syncing with each brutal thrust. He was drowning in the taste of him, the smell of him, the overwhelming reality of being used.

"You love this," Katsuki accused, his thrusts becoming erratic, deeper. "Your fucking body loves it. I can feel your throat milking me. Begging for it."

A raw, broken sound vibrated around Katsuki's cock. Agreement. Surrender. Katsuki's breath hitched, a sharp, ragged thing. "Gonna fill this cocksucker's throat," he promised, the words a hot, filthy whisper. "Gonna paint your guts. You want that? Nod."

Izuku, eyes streaming, managed a feeble nod. The submission shattered the last of Katsuki's control. With a final, deep snarl, he buried himself to the hilt and held, his body going rigid. Izuku felt the hot, pulsing release flood the back of his throat, wave after wave, bitter and claiming.

Katsuki stayed there for a long moment, panting, before slowly pulling out. Izuku collapsed forward, coughing violently, strings of cum and saliva hanging from his ruined lips. He gasped for air, his whole body trembling.

Katsuki looked down at him, tucking himself away with deliberate, satisfied movements. "Lesson three," he said, his voice returning to that chilling calm. "Complete. Your mouth is officially trained." He reached down, not to help, but to tilt Izuku's chin up with two fingers, examining his handiwork. "Clean yourself up."